1. Field
The present disclosure relates to a differential pressure water electrolysis apparatus.
2. Description of the Related Art
For example, hydrogen gas is used as fuel gas for generating electric power in a fuel cell. In general, a water electrolysis apparatus is used to produce hydrogen. This water electrolysis apparatus uses a solid polymer electrolyte membrane (ion-exchange membrane) to decompose water to generate hydrogen (and oxygen). Electrode catalyst layers are provided on both sides of the solid polymer electrolyte membrane to form an electrolyte membrane-electrode assembly, and current collectors are provided on both sides of the electrolyte membrane-electrode assembly to form a unit cell.
A plurality of unit cells are stacked to form a cell unit. A voltage is applied to both ends in the stacking direction of the cell unit while water is supplied to the current collectors on the anode side. Thus, on the anode side of the electrolyte membrane-electrode assembly, the water is decomposed to produce hydrogen ions (protons). The hydrogen ions move through the solid polymer electrolyte membrane to the cathode side and combine with electrons to produce hydrogen. On the anode side, oxygen produced together with hydrogen is discharged with excess water from the cell unit.
In this equipment, stable electrolysis performance needs to be maintained by applying a constant clamping pressure to the cell unit in the stacking direction. So, for example, in Japanese Unexamined Patent Application Publication No. 2003-160891, as shown in FIG. 5, a clamping apparatus 4 for clamping a stack of an anode main electrode 1, a plurality of unit cells 2, and a cathode main electrode 3 in the stacking direction is provided. The clamping apparatus 4 includes a cylinder 6 having an inlet nozzle 5a and an outlet nozzle 5b for compression fluid, and a piston 8 slidably disposed in a cylinder chamber 6a of the cylinder 6 with O-rings 7 therebetween.
The clamping apparatus 4 applies a pressure higher than the pressure of hydrogen produced during the operation of the water electrolysis cell by a constant clamping pressure, with the piston 8. That is, by adjusting regulating valves (not shown) connected to the inlet nozzle 5a and the outlet nozzle 5b for compression fluid, a constant clamping pressure is secured.